“Republican presidential front-runner Donald Trump on Thursday reposted a tweet from a follower blaming his fall in a new Iowa poll on genetically modified corn that “creates issues in the brain.”

A poll released by Quinnipiac University early Thursday shows Trump trailing retired neurosurgeon Ben Carson by 8 points among likely caucus-goers.

The tweet references Monsanto, a company that pioneered the use of genetically modified organisms (GMO) in farming. GMO farming produces larger crops and saves resources, but critics say food that has been genetically engineered is not safe for consumption.”